Formation of methane-related authigenic carbonates in a highly dynamic biogeochemical system in the Krishna–Godavari Basin, Bay of Bengal
Formation of methane-related authigenic carbonates in a highly dynamic biogeochemical system in the Krishna–Godavari Basin, Bay of Bengal
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DOI：
10.1016/j.marpetgeo.2015.02.034
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发表时间：
2015-06
影响因子：
4.2
通讯作者：
M. Kocherla;B. Teichert;S. Pillai;M. Satyanarayanan;P. Ramamurty;D. J. Patil;A. Rao
中科院分区：
文献类型：
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作者：
M. Kocherla;B. Teichert;S. Pillai;M. Satyanarayanan;P. Ramamurty;D. J. Patil;A. Rao
我们报告称，从孟加拉湾克里希纳-戈达瓦里盆地（K-G 盆地）回收的 11 个岩心中发现了大量自生富铁碳酸盐、高镁方解石 (HMC) 和低镁方解石。这些岩心是作为印度天然气水合物勘探计划的一部分在 R/VMarion Dufresne（MD-161：2007 年 5 月）上在不同环境中收集的，包括土丘（泥底辟）、物质流和半远洋沉积物，水深范围为 647 至 2079 米。自生碳酸盐的尺寸范围为 1 毫米至 12 厘米，并呈现出各种形态，如圆形或片状（微）结核和管状形式。对岩心中的 173 个碳酸盐样品进行了深度分布、矿物学、地球化学和稳定同位素组成的研究。 88 个测量的碳酸盐样品中有 46 个的稳定碳同位素组成约为 -50‰，这可以区分为与甲烷相关的碳酸盐 (HMC)，特别是在站点 8 和 15，但在站点 1、5、9 和 12 的丰度也较低。结果表明，站点 8 和 15 的碳酸盐代表古甲烷渗漏位置。 K-G盆地的许多地点富含铁的碳酸盐岩。它们不同的碳同位素组成表明，可能不仅通过有机物降解导致硫酸盐还原，而且产甲烷作用也是其形成的重要过程。
We report the abundant occurrence of authigenic Fe-rich carbonate, high Mg-calcite (HMC) and low Mg-calcite from 11 cores recovered from the Krishna–Godavari Basin (K–G Basin), Bay of Bengal. The cores were collected as part of the Indian gas hydrate exploration program on board R/VMarion Dufresne(MD-161: May, 2007) in different environments, including mounds (mud diapirs), mass flows, and hemipelagic sediments over a range of water depths from 647 to 2079 m. Authigenic carbonates range in size from 1 mm to 12 cm and display various morphologies like roundish or platy (micro-) nodules and tube-like forms. From the cores, 173 carbonate samples have been investigated for their depth distribution, mineralogy, geochemical and stable isotopic composition. The stable carbon isotopic composition of 46 out of 88 measured carbonate samples are around −50‰ which allows the differentiation into methane-related carbonates (HMC), especially at Sites 8 and 15, but also in low abundance at Sites 1, 5, 9 and 12. Results indicate that the carbonates at Site 8 and 15 represent paleo methane seepage locations. The Fe-rich carbonates occur abundantly at many sites in the K–G Basin. Their varying carbon isotopic composition indicates that probably not only sulfate reduction through organic matter degradation but also methanogenesis are the responsible processes for their formation.